Color, Trace Fossils, Weathering, and Soils Causes of Color Common Trace Fossils Weathering Processes - Physical Weathering - Chemical Weathering Weathering Products - Soils - Paleosols Text: Manual p. 15, 89; Boggs Ch.1,

Causes of Color yellowgoethite, jarositecement brownFe-oxidescement redFe-oxidescement, coatings purplehematite (coarse)cement pinkK-feldspar, hematitecement, framework whitekaolinite, gypsum, no organics cement, bleaching greenglauconite, chlorite, illitecement, framework blackorganics, oil, heavy minerals, pyrite, Mn-oxide cement, framework colormineraloccurrence

Color, Trace Fossils, Weathering, and Soils Causes of Color Common Trace Fossils Weathering Processes - Physical Weathering - Chemical Weathering Weathering Products - Soils - Paleosols Text: Manual p. 15, 89; Boggs Ch.1,

Trace Fossils Ichnofacies (Boggs, p. 118) Environment

Color, Trace Fossils, Weathering, and Soils Causes of Color Common Trace Fossils Weathering Processes - Physical Weathering - Chemical Weathering Weathering Products - Soils - Paleosols Text: Manual p. 15, 89; Boggs Ch.1,

Physical Weathering no change in mineral / chemical composition Physical Weathering: Break-down rock into smaller pieces

Physical Weathering 1. Granite 2. Partially-Weathered Granite 3. Granite Grus

roots / lichens freeze-thaw wet-dry hot-cold Physical Weathering

Exfoliation Enchanted Rock batholith

Physical Weathering Spheroidal Weathering Costa Rica

Physical Weathering Painted Desert, Utah Gullying

Bryce Canyon Physical Weathering

Chemical Weathering alter chemical and mineral composition disrupt fabrics Chemical Weathering: Dissolution and/or crystallization of new minerals

Chemical Weathering Feldspar + H + + H 2 O  kaolinite + silicic acid + K + or Na 2+ Hydrolysis: H + breaks down silicates

Chemical Weathering pyrite Oxidation / Reduction: O alters Fe silicates and S minerals pyrite pyrite  hematite silicate mineral  Fe-oxide

Chemical Weathering Fe-oxide Stains (E. McBride) Bastrop, TX

Chemical Weathering Solution: dissolve in water pyrite (E McBride) Limestone Karen Rills calcite / dolomite gypsum halite

Physical/Chemical Weathering bench slope cliff Differential Weathering Grand Canyon

Physical/Chemical Weathering Differential Weathering “Toadstools” Utah

Physical/Chemical Weathering Differential Weathering burrows

Color, Trace Fossils, Weathering, and Soils Causes of Color Common Trace Fossils Weathering Processes - Physical Weathering - Chemical Weathering Weathering Products - Soils - Paleosols Text: Manual p. 15, 89; Boggs Ch.1,

clastic sediments residues (source rock) secondary minerals ions in solution Weathering Products Soils and Sed. Rocks

Weathering Products Terrigenous Clastic Sediments

Weathering Products Evaporites Death Valley, CA Chemical Sediments courtesy Matt Campbell Cements (M. Campbell)

Soils mineral residues rock fragments organics Horizons Soil Profile

Soils Horizons Soil Profile O - organic matter A - topmost mineral horizon E - (eluvial) leaching B - (illuvial) accumulation C - weathered bedrock R - bedrock

Soils bedrock time climate topography

Pedocal Soils Pedalfer Soils 30 inches of rain per year Soils

color texture structure consistency contacts

Soils Texture

FIGURE 3-26FIGURE 3-26 FIGURE 3-28FIGURE 3-28 FIGURE 3-30FIGURE 3-30 FIGURE 3-29FIGURE 3-29 columnar crumb platy blocky Soils Structure

ClassesDescription Non-plastic A roll 4 cm long and 6 mm thick that supports its own weight held on end cannot be formed. Slightly plastic A roll 4 cm long and 6 mm thick can be formed and, if held on end, will support its own weight. A roll 4 mm thick will not support its own weight. Moderately plastic A roll 4 cm long and 4 mm thick can be formed and will support its own weight, but a roll 2 mm thick will not support its own weight. Very plastic A roll 4 cm long and 2 mm thick can be formed and will support its own weight. Consistency: Plasticity Soils

Standard USDA Soil Description Form Soils

Color, Trace Fossils, Weathering, and Soils Causes of Color Common Trace Fossils Weathering Processes - Physical Weathering - Chemical Weathering Weathering Products - Soils - Paleosols Text: Manual p. 15, 89; Boggs Ch.1,

Paleosols

colors (red, green, purple) root casts caliche vertical streaks mottled bedding

Paleosols Paleosols Painted Desert, AZ

Root Casts Paleosol, near Hunt, TX Paleosols

vertical streaks (bleaching) (E. McBride) Paleosol Bastrop, TX

Paleosols (E. McBride) “terra rossa” fill

Reference Soil Survey Manual, 1993, Soil Conservation Service, USDA Handbook 18.